Shock absorber rubbers: roadside repairs

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Originally Posted by PhilipA

Wayne sorry but I disagree. The nut should be done up until it grounds on the shoulder of the shock. That is what it is there for. Its cowboys who keep rattling for a while that make the nuts hard to shift.
I have never had rubbers die prematurely.

The reason that some shocks do rubbers is that they are far too stiff and destroy RUBBER rubbers. The answer here if you really want such stiff shocks is to repalce with poly rubbers, and introduce harshness.
I bought some TJM shocks many years ago that killed the bushes in about 500Km,When I complained TJM apologised and sent me some poly bushes and a Maglight! I took the shocks out as they were ridiculously stiff.
Regards Philip A

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Philip

I guess we will have to disagree on our thoughts on this matter then.
In over 30 years in the trade,I would have seen many hundreds of shocks that have had the nuts tightened till they run out of thread,and they all have the same problem,they have destroyed the bushes be they rubber or poly.The problem with you scenario is that if it was the case that you just tighten the nuts till they ground on the shoulder of the shock,is that in most cases,the bush has lost most of its compression,and for it to be a uniform compression,then the pins would all have to be uniform in the design along with the size of the bush.Now this is not so,some have longer pins with the unthreaded shoulder located at a different point relative to the base of the pin.
You may notice that shock come with a self locking nut or with 2 nuts,the second being used as a lock nut.The reason for this is to stop the nuts unwinding during use.If the nut was done up to the point where it contacted the unthreaded part of the shaft,there is more than a fair chance that it would bind and not come undone without any locking mechanism.Anyone that does shock nuts up with a rattle gun,certainly would never get near my vehicle.The unthreaded part of the thread is a point where the manufacturers feel that the nut should not be tightened any further,even allowing for adjustments made to slightly compressed bushes during the service life of the shocks.
The last shocks I fitted actually had instructions NOT to do the nut up too tight compressing the bushes.
Compressing the bushes too far will also inhibit the amount of movement you will get from the shock during articulation,as well as place extra strain on the shock shaft.This is particularly noticeable in the rear of Land Rovers,where people are looking for that extra bit of travel in the rear and have fitted pin/pin shocks.
Yes I do agree that poly bushes in shocks do tend to introduce harshness,but this is also true for most other parts of the suspension as well.

Wayne

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Originally Posted by markandsandy

Thanks everyone for the useful suggestions. Given the views that the rubbers should be lasting better, I'm wondering whether the oil leaks we're also having might be contributing to early deterioration of the rubbers (though I don't think the leaks are any more than you'd expect in an old defender). The shocks have only been on the vehicle for about 3 or 4 months, so the rubbers are also only about three/four months old and were installed by a trusted landrover mechanic.

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As I mentioned,there is no way that in that short period of time that it is the fault of the shocks,the fact that you can't undo the nuts easily,confirms that whoever fitted the shocks,whether they are a trusted Land Rover mechanic or not,did so incorrectly,leading to premature bush failure.
There are plenty of people on this forum and on others that run the same shocks,and have so for much longer periods and have not had this sort of failure.

Wayne

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I guess we will have to disagree on our thoughts on this matter then.
In over 30 years in the trade,I would have seen many hundreds of shocks that have had the nuts tightened till they run out of thread,and they all have the same problem,they have destroyed the bushes be they rubber or poly.The problem with you scenario is that if it was the case that you just tighten the nuts till they ground on the shoulder of the shock,is that in most cases,the bush has lost most of its compression,and for it to be a uniform compression,then the pins would all have to be uniform in the design along with the size of the bush.Now this is not so,some have longer pins with the unthreaded shoulder located at a different point relative to the base of the pin.

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The result of leaving bushes loose is that the cup jumps out of the mounting hole on compression/extension and the hole in the mount elongates from wear. The reason for the bushes to be tight is to hold the cups with flange firmly in place. Again I have now driven tens of thousands of kilometers on the worst roads in australia with minimal wear on the mounting plate holes and no bush failure. What you may think of as overcompression may not be as certainly the rubber bushes retain their compliance. the forces involved in suspension deflection are very great as evidenced by the solid rubber bump stops ability to be completely compressed when by feel you would think it impossible.

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for it to be a uniform compression,then the pins would all have to be uniform in the design along with the size of the bush.Now this is not so,some have longer pins with the unthreaded shoulder located at a different point relative to the base of the pin.

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Simple. the bushes that come with the shock are correct for that shock but may not be for all shocks. You should be careful mixing and matching.

I wonder how many of your customers have returned to you next time and needed the shock mount holes welded?
Using your rationale I suppose you do not tighten the nuts on the upper rear shock mounts up to the shoulder either? It seems to me the theory and practice should be the same. Or does a different rule apply to each end?
Regards Philip A

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Originally Posted by PhilipA

The result of leaving bushes loose is that the cup jumps out of the mounting hole on compression/extension and the hole in the mount elongates from wear. The reason for the bushes to be tight is to hold the cups with flange firmly in place. Again I have now driven tens of thousands of kilometers on the worst roads in australia with minimal wear on the mounting plate holes and no bush failure. What you may think of as overcompression may not be as certainly the rubber bushes retain their compliance. the forces involved in suspension deflection are very great as evidenced by the solid rubber bump stops ability to be completely compressed when by feel you would think it impossible.

Simple. the bushes that come with the shock are correct for that shock but may not be for all shocks. You should be careful mixing and matching.

I wonder how many of your customers have returned to you next time and needed the shock mount holes welded?
Using your rationale I suppose you do not tighten the nuts on the upper rear shock mounts up to the shoulder either? It seems to me the theory and practice should be the same. Or does a different rule apply to each end?
Regards Philip A

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Actually,noone mentioned leaving the bushes loose,just not running the nut up till it bottoms out at the end of the thread, compressing the bushes.And there is a major flaw in your theory,where you state that bushes already under compression retain their compliance.As the bush becomes more compressed the force required to begin compressing it further becomes greater,hence why the nut becomes harder to turn as you try and tighten it whislt compressing the bush.Everything has its limits.The same with your analogy with the bump stop.If you had a compressed bumpstop,and then applied more force to it,the bumpstop is going to transfer a lot more of that force than an uncompressed bumpstop would,or the bumpstop will possibly split if it reaches its compression limit.
And working in a professional capacity fulltime,and not just an owner doing their own repairs,I have never had to repair shock mount holes on anyones vehicle that I have fitted shocks to.
As I have said,I base my results on well over 30 yrs of experience working in the field.And as well as that ,I have had 4wd vehicles of many types since 1971,and not one has chopped out a shock mount.And I might have done a few miles in that time as well;).
Just so this goes no further.I will just agree to disagree with your method and rational.

Wayne

Just to confuse the issue further :p.

Rubber is basically incompressible. It will distort easily, but won't compress.

Not sure what size rubbers you have but sometimes when no new rubbers avalable I've used milking machine rubberware as a replacement . Lasted longer than proper stuff and it was used. Change rubberare every 6 months so there's a lot to through away. Makes exelent bushes

Gary

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Originally Posted by 33chinacars

Not sure what size rubbers you have but sometimes when no new rubbers avalable I've used milking machine rubberware as a replacement . Lasted longer than proper stuff and it was used. Change rubberare every 6 months so there's a lot to through away. Makes exelent bushes

Gary

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If needs must the sidewall of a tyre (obviously a discarded one) can also be fashioned into a half decent bush when on your travels.

stacking various diameter rubber hose inside each other then trimming to length also works quite well.

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Originally Posted by LowRanger

Actually,noone mentioned leaving the bushes loose,just not running the nut up till it bottoms out at the end of the thread, compressing the bushes.And there is a major flaw in your theory,where you state that bushes already under compression retain their compliance.As the bush becomes more compressed the force required to begin compressing it further becomes greater,hence why the nut becomes harder to turn as you try and tighten it whislt compressing the bush.Everything has its limits.The same with your analogy with the bump stop.If you had a compressed bumpstop,and then applied more force to it,the bumpstop is going to transfer a lot more of that force than an uncompressed bumpstop would,or the bumpstop will possibly split if it reaches its compression limit.
And working in a professional capacity fulltime,and not just an owner doing their own repairs,I have never had to repair shock mount holes on anyones vehicle that I have fitted shocks to.
As I have said,I base my results on well over 30 yrs of experience working in the field.And as well as that ,I have had 4wd vehicles of many types since 1971,and not one has chopped out a shock mount.And I might have done a few miles in that time as well;).
Just so this goes no further.I will just agree to disagree with your method and rational.

Wayne

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As much as I hate to agree with Phillip "let's mine the GBR for oil for a quick buck, despite it being worth $6Billion P.A. for tourism" A, he is 100% correct, despite your purported years of experience. IME shocks with a pin-end have a pronounced step, to ensure the nut cannot be tightened more or less than is required. The shock is designed such that the nut is tightened hard up against the step. I would like to see you produce any documentation from a shockie manufacturer to show otherwise...

FWIW, every 109" landie I have worked on has needed the shockie holes in the axle welded up, despite the bolt being fastened correctly.